Bipolar electrolytic diaphragm cell having friction welded conductor/connector means

ABSTRACT

A BIPOLAR ELECTROLYTIC DIAPHRAGM CELL IS DISCLOSED HAVING A LOW RESISTANCE CONDUCTOR-CONNECTOR BETWEEN THE CATHODES OF ONE CELL AND THE ANODES OF THE NEXT ADJACENT CELL. THE CONDUCTOR/CONNECTOR, WHICH PENETRATES THROUGHT THE BACKPLATE, HAS AN ANOLYTE-RESISTANT MEMBER CONNECTED TO THE ANODE AND A CATHOLYTE-RESISTANT MEMBER CONNECTED TO THE CATHODE. THE ANOLYTE- AND CATHOLYTE-RESISTANT MEMBERS ARE CONNECTED TO AN INTERMEDIATE HIGH CONDUCTIVITY MEMBER BY FRICTION WELDING.

IL.GUNBY May 28, 1974 APHRAGM CELL HAVING FRIC WELDEDCONDUCTOR/CONNECTOR MEANS TION BIPOLAR ELECTROLYTIC DI 4 Sheets-Sheet 1Filed Nov. 24, 1972 nunnn 2 unnn I I I U I 5- var-bah. r 9..

May 28, 1974 G N Y 3,813,326

BIPOLAR ELECTROLYTIC DIAPHRAGM CELL HAVING FRICTION WELDEDCONDUCTOR/CONNECTOR MEANS Fj led Nov. E4 1972 F'nc 3 4 Sheets-Sheet May28, 1974 1.. GUNBY 3,313,325

BIPOLAR ELECTROLYTIC DIAPHRAGM CELL HAVING FRICTION WELDEDCONDUCTOR/CONNECTOR MEANS F)" led Nov. 24, 1972 4 Sheets-Sheet 4 UnitedStates Patent BIPOLAR ELECTROLYTIC DIAPHRAGM CELL HAVING FRICTION WELDEDCONDUCTOR/ CONNECTOR MEANS Leslie Gunby, Pittsburgh, Pa., assignor toPPG Industries, Inc., Pittsburgh, Pa. Filed Nov. 24, 1972, Ser. No.309,310 Int. Cl. B011: 3/00 US. Cl. 204-268 21 Claims ABSTRACT OF THEDISCLOSURE A bipolar electrolytic diaphragm cell is disclosed having alow resistance conductor/connector between the cathodes of one cell andthe anodes of the next adjacent cell. The conductor/connector, whichpenetrates through the backplate, has an anolyte-resistant memberconnected to the anode and a catholyte-resistant member connected to thecathode. The anolyteand catholyte-resistant members are connected to anintermediate high conductivity member by friction welding.

BACKGROUND OF THE INVENTION Bipolar electrolytic diaphragm cells, usefulin the electrolysis of brines, e.g., aqueous solutions of alkali metalhalides such as sodium chloride, have a plurality of individualelectrolytic cells in bipolar mechanical and electrical configuration.The structure for eifecting bipolar mechanical and electricalconfiguration is an electroconductive, electrolyte-resistant backplateseparating the adjacent cells from one another, and serving as astructural member for the cathodes of one cell and the anodes of thenext adjacent cell in the bipolar electrolyzer.

The backplate has three functions. First, the backplate separates thecatholyte of one cell from the anolyte of the next adjacent cell of theelectrolyzer. Second, the backplate is a conductive member connectingthe cathodes of one electrolytic cell and the anodes of the nextadjacent cell in the electrolyzer, thereby providing bipolar electricalconfiguration between the cathodes of one cell and the anodes of thenext adjacent cell in the electrolyzer. Third, the backplate acts as acommon structural member, having cathodes extending substantiallyperpendicularly from one side and anodes extending substantiallyperpendicularly from the other side, thereby providing bipolarmechanical configuration.

In the design and construction of bipolar diaphragm electrolyzers, it isparticularly important to conduct current from the cathodes of the onecell to the anodes of the next adjacent cell with the minimum voltagedrop between cells. This voltage drop is a combination of IR voltagedrop and contact resistance voltage drop. This minimization of voltagedrop must be accomplished with the minimum amount of seepage ofelectrolyte through the backplate from the electrolyte of one cell tothe electrolyte of the adjacent cells. The minimization of IR dropthrough the backplate and the minimization of contact resistance betweenthe cathodes of one cell and the anodes of the next adjacent cell whilemaintaining the structural integrity of the backplate, are particularlyimportant goals. This is because a typical electrolyzer may contain aplurality of cells, for example, from 3 to 8 or 11 or more cells, forexample, as many as 70 or 80 cells. Additionally, electrolyzers arefrequently connected in series, thereby providing as many as three orfour hundred individual cells in a series. Bipolar electrolyzersfrequently operate at high currents; for example, 70,000, 100,000, oreven 150,000 amperes. Thus, it can be seen that a voltage reduction ofonly ten one-thousandths of a volt per cell may result in an overallvoltage savings of 3 or more volts 3,813,326 Patented May 28, 1974 iceacross an entire cell circuit and a power savings of as much as threehundred kilowatts across the entire cell circuit.

Early attempts to conduct current from the cathode of one cell to theanode of the next adjacent cell in an electrolyzer with minimum IR andcontact resistance voltage drops and substantially no seepage ofelectrolyte between electrolytic cells generally required means forconducting electricity from a cathode of one cell through the backplateto an anode of the next adjacent cell, and for connecting the anode andcathode to the backplate, which breached the backplate. Suchconductor/connectors had a conductive material, for example, copper,sheathed in a catholyte-resistant metal, such as steel, on one side ofthe copper, and an anolyte-resistant metal, such as titanium, on theother side of the conductor. The titanium sheathing was typically silverwelded to the copper conductor using a 99.99 percent pure siver filler,and the steel sheathing was typically welded to the copper conductorusing a copper-silicon filler metal. The silver Welded joints werecharacterized by high cost, and a substantial degree ofnon-reproductibility, thereby necessitating percent inspection of all ofthe joints. Furthermore, the means provided for complete inspection ofall soldered joints were themselves subject to occasional failure,allowing electrolyte to attack the copper conductor, raising the voltagedrop across the cell, and ultimately leaking into the eletcrolyte of theadjacent cell, and causing failure of the conductor/connector.

SUMMARY OF THE INVENTION It has now been found that a means, hereinaftercalled a conductor/connector, for conducting electricity from a cathodeof one cell through a common backplate to an anode of the next adjacentcell, and connecting the anode and cathode to the common backplate,where both an anolyte-resistant member, and a catholyte-resistantmember, including sheathing, are friction-welded to an intermediatemember of high conductivity, provides a particularly outstandingconductor/connector. Friction-welded conductor/connectors arecharacterized by the absence of a third phase between the joined pieces,a high degree of reproducibility of the voltage drop across theconductor/ connector, and a considerable cost savings in fabrication.Additionally, the friction-welded conductor/connector is substantiallyless subject to attack by electrolyte than the siver weldedconductor/connectors, and may be prepared at significantly lower cost.

According to this invention, a conductor/connector is provided having acopper current-conducting member. At one end of the current-conductingmember, the anodic end, is a friction-welded member of ananolyte-resistant metal. At the other end of the conductor/connector,the

cathodic end, is a catholyte-resistant member which also extends alongthe sides of the copper conductor as a sheath or sleeve to protect thecopper from the catholyte.

DESCRIPTION OF THE INVENTION Specific exemplifications of the inventiondisclosed herein may be more fully understood by reference to thefigures.

FIG. 4 is a cutaway drawing showing a side-by-side comparison of theconductor/connector described in the prior art, FIG. 4A, and aconductor/connector of the type described herein, FIG. 4B.

FIG. is a schematic flow diagram for a method of preparing a backplatefor a bipolar electrolyzer according to the method described herein.

A typical bipolar electrolytic diaphragm cell is shown in schematicexploded view in FIG. 1. The cell has a cell box 101 containing theindividual electrolytic cells. While a single cell box is shown, theremay alternatively be a plurality of individual cell boxes. For purposesof illustration, three cells are shown inside the cell box. Each of theindividual bipolar cells has a backplate 1 with a cathodic surface 5 ofa catholyteresistant metal and an anodic surface 9 of ananolyte-resistant material. Extending perpendicularly from the cathodicsurfaces 5 of the backplate 1 are cathodes 37. Extending perpendicularlyfrom the anodic surfaces 9 of the backplate 1 are anodes 21. The anodesare interleaved between the cathodes 37 of the next backplate.

FIG. 2 is an isometric, partial cutaway view of a single backplate of anelectrolytic cell, and FIG. 3 is a cutaway along plane 33' of FIG. 2.The backplate has anodes 21 and cathodes 37 connected thereto. Thebackplate 1 has a cathodic surface 5 and an anodic surface 9 asdescribed above. The cathodes 37 extend from the cathodic surface 5 ofthe backplate 1, and have mesh fingers 41 covered with a diaphragm 53.The diaphragm may be an asbestos diaphragm, an electrolyte-permeableresin, or a permionic membrane. The cathodes 37 are supported on a steelbase 45 which is bonded to the conductor/connector 61 and have areinforcing member 49 to prevent collapse during diaphragm pulling. Acathodic backscreen 57, also covered with a diaphragm 53, separates theindividual cell into anolyte and catholyte compartments. The backscreen57 is mounted on the backplate 1 of the cell on the cathodic side 5thereof.

The anodes 25 are connected to the anolyte surface 9 of the backplate 1.The anodes 21 extend perpendicularly from the backplate and areinterleaved between the cathodes of the next adjacent backplate in theseries as shown in FIG. 1 above. The anodes themselves may either begraphite anodes or they may be of the metal type known in the art asdimensionally-stable anodes. Such dimensionally-stable anodes have anelectroconductive surface, e.g., a platinum group metal, an oxide of aplatinum group metal, an anolyte-resistant conductive oxide of a metal,an anolyte-resistant, conductive oxide of several metals, or the like,on a valve metal base. The valve metals are those metals which form anon-conducting oxide which is resistant to the anolyte when exposed tothe anolyte. The valve metals include titanium, zirconium, hafnium,vanadium, niobium, tantalum, and tungsten. The anodes are typically inthe form of blades 25 and a base 29. The blades 25 may be perforate orforaminous. The anodes may be a single blade between two cathode fingersor two blades interposed between a pair of cathode fingers. In the caseof two blades 25 interposed between a pair of cathode fingers 41, theanode blades 25 may be coated on only the surfaces facing the cathodes45, or only on the surfaces within the anode between the two anodeblades, or on both sets of surfaces. The anode base 29 is bonded to aconductor 33 of the conductor/connector 61.

In FIG. 2, the conductor/connector 61 is shown extending through thebackplate 1 bonded to the steel base 45 of the cathode 41 and theconductor 33 at the base of the anode 29.

The conductor/connector is shown in more detail in FIG. 3. Theconductor/connector 61 breaches the backplate 1 of the electrolyticcell. In one preferred exemplification, the conductor/connector 61 has acylindrical copper stud 65 extending through the center thereof. On theanodic side of the copper stud 65 is an anolyte-resistaut conductor 33.On the cathode side of the copper studs 65 is a catholyte-resistantmember 45.

The bond between the anolyte-resistant member 33 of theconductor/connector 61 and the copper member 65 typically has aconductivity of greater than 1.5x 10 mho when measured by leads one halfof an inch from the bond in a 0.75 inch diameter piece. Generally, theconductivity is between 1.6)(10 and 5.0)(10 mho, and most frequently,the bond has a conductivity of from about 3.0)(10 mho to about 3.6 l0mho, although conductivities of as high as 10 mho or even higher may beattained.

Thus, according to this invention, a conductor/connector is providedhaving a voltage drop of less than 25 milli- -volts at a current flow of400 to 500 amperes. The bond is further characterized by the completeabsence of a slag, solder, or welding flux containing third phasebetween the anolyte-resistant member 33 and the copper member 65. Thebond is also characterized by the substantial absence of a third phasecontaining an alloy or intermetallic compound of copper and the metalused in fabricating the anolyte-resistant member 33. Such an alloy orintermetallic compound-containing phase if present at all, is notdetectable by optical examination at 1000 magnification.

As will be described more fully hereinafter, in a preferredexemplification of this invention the anolyte-resistant member 33 isfriction-welded to the copper stud 65.

The catholyte-resistant member 45 may be friction-welded to the copperstud 65 or it may be bonded thereto by another means.

A catholyte-resistant sheave or sleeve 77 shields the While the copperconductor 65 is spoken of and illustrated as being a cylindrical stud,other geometries may be used. Thus, the copper conductor 65 may be amachined hexagonal or rectangular stud.

According to one preferred method of utilizing the, conductor/connectorof this invention, the sheathed conductor/connector 61 is placed throughan opening in the catholyte-resistant member 5 of the backplate 1 withthe sheath inserted to a depth sufiicient to provide some rigidity tothe conductor/connector 61. The sheath is welded to the backplate. Aconcentric member 13 such as a copper washer, fits in contact with thebackplate and concentric with the center-line of the conductor/connector61, although not necessarily contacting the anolyteresistant member 33-.The anolyte-resistant member 9 of the backplate 1 fits around theanolyte-resistant member 33 of the conductor/connector 61, separatedfrom the catholyte-resistant member 5 of the backplate 1 by theconcentric member 13. The concentric member 13 serves to separate theanolyte-resistant member 9 of the backplate 1 from thecatholyte-resistant member 5 of the backplate 1 in order to allow forthe recombination of atomic hydrogen evolved at the catholyte surface ofthe catholyte-resistant member 5 of the backplate 1 which atomichydrogen thereafter permeates through the catholyte-resistant member ofthe backplate, as more fully described in the commonly assignedapplication of Carl W. Raetzsch et a1., Ser. No. 158,695, filed July 1,1971, now Pat. No. 3,759,813 for an Electrolytic Cell.

The anolyte-resistant member 9 of the backplate 1 may be bonded to theanolyte-resistant member of the conductor/connector 61 by any meansknown in the art such as butt welding, resistance welding, flashwelding, heliarc welding, or the like. Or, as shown in the figures, theanolyte-resistant member 33 of the conductor/connector 61 may be bondedto an anolyte-resistant concentric member 17 which is in turn bonded tothe anolyteresistant surface 9 of the backplate 1.

FIGS. 4A and 4B are a side-by-side comparison of the conductor/connectorof the prior art and one exemplification of the conductor/connectordescribed herein. Both the prior art conductor/ connector and theconductor/com nector described herein are shown in combination with abackplate 1 having a cathodic 5 and an anodic surface 9 separated fromthe cathodic member 5 by a copper washer 13. At the cathodic end of bothconductor/connectors is a steel cathode base 45. At the anodic end ofboth conductor/connectors is an anode base 29 which is bonded to ananolyte-resistant conductor 33 and 133 in both the conductor/connectordescribed herein and the conductor/ connector of the prior art.

Both the prior art conductor/connector and the conductor/connectordescribed herein have a copper stud 65 encased in a catholyte-resistantsleeve or sheath 77 which sleeve or sheath is bonded to thecatholyte-resistant member 5 of the backplate 1. Both the prior artconductor/ connector and the conductor/connector described herein arebonded to the anolyte-resistant member 9 of the backplate 1. As shown inFIG. 4B, this may be accomplished by bonding the anolyte-resistantmember 33 of the conductor/connector 61 to an anolyte-resistantconcentric member 17 such as titanium washer, which concentric member 17is then bonded to the anolyte-resistant surface of the backplate.

In the conductor/ connector of the prior art, the anolyteresistantmember 134 is an anolyte-resistant nut which is bolted to a threadedcopper stud 65. It has been found that in order to obtain satisfactoryconductivity, the anolyte-resistant titanium nut 134, afer being boltedto the copper stud, must be silver welded thereto. The anolyte-resistantnut cap 133 is titanium welded or otherwise suitably bonded to thetitanium nut 134. On the cathodic side of the prior artconductor/connector, the copper stud 65 is welded to thecathoylte-resistant sleeve 77 and the catholyte-resistant sleeve 77 issilver welded 173 to the catholyte-resistant member 45.

The exemplification of the conductor/connector described herein is shownin FIG. 4B. As can be seen therein, the anolyte-resistant conductors 33and copper studs 65 have an interface 69 therebetween. This interface isthe site of the friction weld. There is also an interface between thecopper stud 65 and the catholyte-resistant member 45. This interface 73may be provided by conventional welding techniques, or by frictionwelding. In a preferred exemplification of this invention, the bond atthe interface 73 between the copper stud 65 and the catholyte-resistantmember 45 is provided by a friction welding. A friction weldedcopper-titanium typically has a resistance of from about 28 10 ohm toabout 30 1-0- ohm when tested by applying probes 0.5 inch on either sideof the joint on a 0.75 inch diameter piece. There is also a jointbetween the sleeve or sheath 77 and the catholyte-resistant member 45.This joint may be provided by friction welding or by other bondingmethods.

Conventional means of welding do not provide a satisfactory bond betweencopper and titanium. Conventional flux welding techniques and moltenmetal welding techniques provide an undesirable third phasecharacterized by a high degree of non-reproducibility of the electricalresistivity and a marked decrease in strength. One way to overcome thesedifficulties in providing a suitable titanium to copper bond is toutilize welding techniques with filler wire characterized by a highelectrical conductivity, such as silver filler wire. However, suchsilver welded copper-titanium joints are not readily reproducible, anddo not have constant voltage drop from joint to joint.

Satisfactory, high conductivity welds of copper to titanium are providedby welding techniques characterized by the substantial absence of eithera flux or of a molten metal phase during welding. Such techniquesinclude friction welding, ultrasonic welding and detonation welding.Friction welding, also known as inertial welding, is particularlysatisfactory for providing a high conductivity copper-titanium joint.The copper-titanium joint is characterized by a high degree ofreproducibility of the electrical conductivity from weld to weld, andrequires a lower degree of quality control than copper-titanium bondingtechniques of the prior art. Friction welding makes use of thefrictional heat generated at the forging surfaces of two workpieces,when the two workpieces are revolved relative to one anotherand thenpressed against one another. The speed of revolution and the imposedpressure are such as to evolve suflicient heat to raise the temperatureof the two workpieces above the extrusion or softening temperature ofthe workpeices, thereby plasticizing the butting areas or forgingsurfaces, but below the melting temperatures of the workpieces, therebyavoiding the formation of a liquid phase. When the butting areas becomeplastic, or extrudable, the rotational force, or torque, is halted andthe imposed pressure increased to form a'joint.

' The friction-welded joint is characterized by the existence of acollar of extruded metal around the joint. Additionally, the completedworkpiece is characterized in that its length is less than the sum ofthe original length of the two workpieces. This diminution in length,which occurs during the formation of the collar is called the upset.

Friction welding, for example of copper to titanium, or of steel tocopper, is a three-stage process. Each stage is characterized by adistinctive torque, feed pattern, and temperature pattern.

The first stage of friction welding is evidence by a low torque andincreasing temperature. The onset of the second stage is evidenced by atrend of unevenly increasing torque and increasing temperature. Duringthe second stage the torque reaches a maximum. The third stage isevidenced by upset as the collar forms around the weld.

These three stages are described in the literature, e.g., T. T.Houldcroft, Welding Progress, Cambridge University Press (1967), pp.178-182; F. Koenigsberger and J. R. Adair, Welding Technology, 3rd Ed.,MacMillan Company (1966), pp. 182-192; and V.I. Vill, Theory of FrictionWelding, American Welding Society Translation (1962).

The first stage is reported in the literature as being characterized bythe collision and erosion of high spots, the rupturing of oxide filmssuch as the TiO,, film, and metal to metal contact as the rotatingbodies are subjected to dry friction. The second stage, a stage ofunevenly increasing torque, is reported as being characterized byseizure, i.e., the formation of metal to metal bonds, and shear, i.e.,the breaking of these metal to metal bonds. According to the literature,the seizure or making of the metal to metal bonds transforms the kineticenergy into chemical energy (heat of formation), while the shear orbreaking of the bonds transforms the chemical energy into sensible heat,which in turn heats the workpieces. In this way, the second stage is astage of increasing temperature of the forging surfaces. The thirdstage, characterized by upset and the formation of the collar, isdescribed in the literature as occurring when the temperature is highenough that the compressive strength becomes less than the imposedshear. In this stage, the temperature of the workpieces is below themelting temperature of the lower melting of the two workpieces, butabove their extrusion or softening temperatures.

During the third stage, the actual welding of the titanium and copperoccurs. In the friction welding of titanium to copper, a large upset,e.g., from about 0.050 inch to about 0.100 inch is preferred. Upsets ofa lesser amount, e.g., less than about 0.025 of an inch, whilesatisfactory in providing a physically strong weld, may not remove allof the oxide from the interface, and may therefor provide a lowerconductivity. Upsets of greater than about 0.0125 inch, while notdeleterious, do not sufficiently improve the conductivity or mechanicalstrength in order to justify the additional torques or imposed pressuresnecessary therefor.

During the first two stages of friction welding, increasing therotational velocity decreases the time necessary to attain the onset ofthe third stage. Similarly, decreasing the angular velocity increasesthe time necessary to attain the onset of the third stage.

While the duration of the third stage is reported in the literature asbeing essentially independent of the rotational velocity, the quality ofthe weld is reported to be a function of the rotational velocity duringthe third stage. Too low a rotational velocity may result in a weld atthe periphery only and not at the center of the surfaces to be welded.This is because frictional welding starts at the perimeter of thesurfaces to be friction welded and works toward the center. A completeweld, through to the center, requires a high rotational velocity.

In the friction welding of copper to titanium, particularly good resultsare obtained if the rotational velocity is from about 1000 to about 5000revolutions per minute and generally from about 2000 to about 3000revolutions per minute, and especially about 2500 revolutions perminute. Particularly good results are obtained when the imposed pressureis from about 5000 to about 15,000 pounds per square inch and especiallyabout 10,000 pounds per square inch during the first two stages. In thefriction welding of titanium to copper, upset may occur without anincrease in pressure during the third stage.

While the above pressures and rotational velocities are optimum rangesthereof, the determination of particular pressures and rotationalvelocities within these ranges are matters of mere routine testing. Withrespect to the upper ranges of rotational velocity, the process offriction welding is repeated to be essentially self-regulating. That is,if the rotational velocity is too high and a molten metal film isformed, the molten metal, having a lower coefiicient of friction, actsas a lubricant, cooling and ultimately resolidifying.

FIG. shows a schematic flow chart for a method for preparing a backplateaccording to the method of this invention. As shown therein, a copperstud 65 is friction welded to a titanium member 33 as describedhereinbefore. Thereafter, a catholyte-resistance member 45 such as asteel cap or stud is bonded to the opposite surface of the copper stud.This may be either by conventional copper-iron welding techniques, oralternatively, by friction welding. Thereafter, the catholyte-resistantsleeve or sheath 77 is slid over the copper and titanium stud and bondedto the catholyte-resistant member, e.g. a steel cap 45. This may be byfriction welding or by conventional steel welding techniques.

The conductor/connector 61, a copper stud 65 with a steel cap 45 andsheath 77 bonded to one end thereof, and a titanium stud 33 frictionwelded to the other end thereof, is inserted in the steel member 5 ofthe backplate 1, with the catholyte-resistant cap 45 and sleeve 77protruding through the cathodic surface 5 of the backplate. The sleeve77 is welded to the backplate 1, for example, with a weld of the typeshown in FIG. 3 herein above. A fitting 13 such as acopper washer isthen placed around the conductor/connector on the opposite side thereofin contact with the opposite surface of the cathodic member of thebackplate 1. The anolyte-resistant member 9 of the back plate 1 isplaced on the catholyte-resistant member 5 of the backplate with theconductor/connector 61 protruding through an opening in theanolyte-resistant member 9 of the backplate 1. Thereafter, ananolyteresistant fitting such as a titanium washer 17 of FIGS. 3 and 4is welded to the titanium stud thereby holding the anolyte-resistant 9and the catholyte-resistant 5 members of the backplate 1 in compression.

While FIG. 5 illustrates one order of assemblying theconductor/connector, other orders of assembly may be followed. Forexample, the sheath or sleeve 77 and the copper stud 65 may be frictionwelded to the catholyteresistant member 45 simultaneously. Theanolyte-resistant member 33 may be friction welded to the copper stud 65either before or after the sheath or sleeve 77 and catholyte-resistantmember 45 have been welded to the copper stud 65.

It should be noted that various elements of the backplate may bedispensed with or modified. For example, in a back plate 1 having twodistinct members, the steel sheath or sleeve 77 may be welded to eitherthe cathodefacing surface of the catholyte-resistant member, or to theanolyte-facing surface of the catholyte-resistant member, or to bothsurfaces. Additionally, the sheath or sleeve 77 may extend the fulldepth of the catholyteresistant member or only to the cathodefacingsurface of the catholyte-resistant member, or to an intermediate lengththerein. The sheath 77 of the conductor/connector 61 may be weldeddirectly to the catholyte-resistant member of the backplate 1, oralternatively, it may be welded or bonded to a washer-type fitting,which is in turn welded or suitably bonded to the catholyte-resistantmember of the backplate. The washer or spacer between thecatholyte-resistant member of the backplate 5 and the anolyte-resistantmember 9 may be dispensed with, and the two members 5 and 9 of thebackplate 1 may be in direct physical contact with each other.

According to another exemplification of this invention, the backplatemay be a bonded steel-titanium backplate fabricated from Detaclad(trademark) as described in US. Pat. 3,137,937 to Cowan et al. In such acase, the sleeve or sheath 77 would only extend a fraction of the depthof the backplate.

Additionally, the anolyte-resistant member 33 of the conductor/connector61 may be bonded directly to the anolyte-resistant member of thebackplate 9 or it may be bonded to an anolyte-resistant fitting 17 whichis in turn bonded to the anolyte-resistant member 9 of the backplate 1.The anodes may be bonded directly to the anolyte-resistant member 33 ofthe conductor/connector, or there may be an intermediate membertherebetween, such as an anode bar or anode base member. Similarly, thecathodes 37 may be bonded to the cathode bars, resistant member 33 ofthe conductor/connector 61, or the cathode 37 may be bonded to thecathode bars, cathode connectors, cathode bases or the like, which arein turn bonded to the catholyte-resistant member of theconductor/connector of this invention.

After assembly of either the individual conductor/ connector, or of anentire backplate, quality control may be exercized by measuring thevoltage drop. At a current load of 400 to 500 amperes across theconductor/connector the voltage drop should be less than 25 millivolts.

While this invention has been described with particular reference tobipolar chlor-alkali electrolytic diaphgram cells, its use is notintended to be so limited thereby. Friction welded conductor/connectorsof two dissimilar metals, e.g., titanium and copper, may be used in anybi polar electrolytic cell having dissimilar electrolytes separated by adiaphragm or membrane wherein a high conductivity between two dissimilarmetals is necessary. For example, the conductor/connector of thisinvention may be used in bipolar fuel cells having a membrane separatingthe anodic compartment from the cathodic compartment of one cell andrequiring a conductor having anolyte-resistant and catholyte-resistantfaces for connecting one set of electrodes of opposite polarities in thenext adjacent cell through a common backplate. Friction weldedconductor/connectors may also be used in bipolar electrolytic cells,generally, such as electrolytic cells for the production of sodiumchlorate.

The following example is illustrative.

EXAMPLE I A pilot plant bipolar diaphragm electrolyzer containing twobipolar backplates is constructed to test the effects of different typesof conductor/connectors. Each individual diaphragm cell has a backplatewhich is a 1.00 inch thick Type A36 steel plate functioning as acathodic member and a 0.040 inch thick titanium sheet functioning as ananodic surface. The cathodic member is separated from the anodic memberof the backplate a hi inch thick copper washer between the titaniummember and steel member. The anodes are expanded mesh A.S.T.M. B265Grade One titanium having a platinum-iridium surface thereon. Thecathodes are A.I.S.I. 1005 steel, 6 x 6 mesh inch double crimped 13guage wire calendered to inch thick. The cathodes have identicalasbestos diaphragms pulled from Johns-Manville type 3T-4T absestos agedin a cell liquor solution.

In one electrolytic cell, the conductor/connectors are of the type shownas representative of the prior art on the left-hand side of FIG. 4,having a 3.8225 inch long by 0.75 inch diameter coper conductor threadedat the anode end thereof. The threading in UNC threads per inch for 1.0inch. The conductor/connector has a steel sleeve on the cathode end anda inch thick by 1.0 inch wide by 6 inch long steel bar silver-welded tothe open end of the sleeve.

This procedure is followed with all of the conductor/ connectors. Theconductor/connectors are welded into openings in the backplate prior toassembling the nut and cap. Then the copper washer is placed on theopposite surface of the steel member of the backplate and the 0.040 inchthick titanium sheet is placed against the cop per washer. Afterassembly an A.S.T.M. B265 Grade One titanium nut is bolted to thethreaded copper stud and silver welded thereto. The nut is also titaniumwelded to the titanium sheet using a titanium filler wire. A titaniumcap is then titanium welded to the open end of the titanium nut. At acurrent of 408 amperes through the conductor/connector, the voltage dropacross the welded conductor/connnector is 15.2 millivolts. The anodesand cathodes are then welded to the conductor/ connectors.

Another backplate for an electrolytic cell is prepared having frictionwelded conductor/connectors between the cathode of one cell and theanode of the next adjacent cell. The conductor/connectors have a 0.5inch diameter by 3.4375 inch long copper stud friction welded to a 0.8inch diameter by 0.375 inch long A.S.T.M. B265, Grade One titanium cap.The friction welding of the titanium to the copper is conducted at arotational velocity of 2500 revolutions per minute and a forge pressureof 10,000 pounds per square inch. An upset of about 0.075 inch isobtained.

A Type A36 steel bar inch thick by 1% inches wide by 6 inches long isfriction-welded to the opposite surface of the copper rod. Thereafter, asteel sleeve is friction welded to the steel bar providing acatholyteresistant surface around the copper member of theconductor/connector. This procedure is followed with all of theconductor/connectors. The voltage drop across the friction weldedconductor/connector is 14.4 millivolts at 408 amperes.

The conductor/connectors are then welded into openings in the backplate,a copper washer is placed on the opposite surface of the steel member ofthe backplate and the 0.040 inch thick titanium sheet, as describedabove, is placed against the steel member of the backplate. A titaniumwasher is then placed around the titanium member of theconductor/connectors and welded thereto and to the backplate by titaniumwelding. The anodes and cathodes are welded to the conductor/connectoras described hereinabove.

The electrolyzer is then assembled and electrolysis is commenced with abrine feed containing about 310 grams per liter of sodium chloride beingfed to the electrolytic cell.

Although the invention has been described with reference to particularspecific details and contains preferred exemplifications, it is notintended to thereby limit the 10 scope of this invention except insofaras the details are recited in the apended claims:

What is claimed is:

1. In a bipolar electrolyzer having a plurality of electrolytic cells inseries, with cathodes of one cell and the anodes of the next adjacentcell in the electrolyzer supported upon a common, electrolyte/resistantstructural member, in bipolar electrical and mechanical configurationwith each other, the said structural member having means for connectingsaid anodes and cathodes to said backplate and conducting electricityfrom said cathodes to said anodes, the improvement wherein saidconnecting and conducting means comprise:

a copper member;

a cathoylte-resistant member bonded to the cathode and of said coppermember; and

an anolyte-resistant member friction welded to the opposite end of saidcopper member.

2. The bipolar electrolyzer of claim 1 wherein the saidcatholyte-resistant member is friction welded to said copper member.

3. The bipolar electrolyzer of claim 1 wherein the friction welded bondbetween the anolyte resistant member and the copper member of saidconducting and connecting means has an electrical conductivity ofgreater than about 1.5)(10 mho measured one-half inch from each side ofthe bond.

4. The bipolar electrolyzer of claim 1 wherein the saidcathoylte-resistant member on the cathode-facing end of said coppermember is a steel member.

5. The bipolar electrolyzer of claim 1 wherein a cathode is bonded tothe catholyte-resistant member of said connecting and conducting means.

6. The bipolar electrolyzer of claim 1 wherein the saidanolyte-resistant member is a titanium member.

7. The bipolar electrolyzer of claim 1 wherein an anode is bonded tosaid titanium member.

8. In a bipolar electrolyzer having a plurality of electrolytic cells inseries, with the cathodes of one cell and the anodes of the nextadjacent cell in the electrolyzer supported upon a common,electrolyte-resistant structural member, in bipolar electrical andmechanical configuration with each other, the said structural memberhaving means for connecting anodes and cathodes to said backplate andconducting electricity from said cathodes to said anodes, theimprovement wherein said connecting and conducting means comprises:

a copper stud;

a catholyte-resistant sleeve on said copper stud;

a catholyte-resistant member on the cathode end of said sleeve and saidstud; and

a titanium stud friction welded to said copper stud wherein saidtitanium stud is bonded to said anode and said catholyte-resistantmember is bonded to said cathode.

9. The bipolar electrolyzer of claim 8 wherein the saidcatholyte-resistant member is friction welded to said copper stud.

10. The bipolar electrolyzer of claim 8 wherein the friction welded bondbetween the anolyte resistant member and the copper member of saidconducting and connecting means has an electrical conductivity ofgreater a about 1.5 10 mho measured one-half inch from each side of thebond.

11. The bipolar electrolyzer of claim 8 wherein the saidcatholyte-resistant sleeve is a steel sleeve.

12. The bipolar electrolyzer of claim 8 wherein the saidcatholyte-resistant member on the end of said catholyteresistant sleeveis a steel member.

13. The bipolar electrolyzer of claim 8 wherein an anode is bonded tosaid titanium stud.

14. The bipolar electrolyzer of claim 8 wherein a cathode is bonded tothe catholyte-resistant member of said connecting and conducting means.

15. In a bipolar electrolyzer having a plurality of electrolytic cellsin series, with the cathodes of one cell and the anodes of the nextadjacent cell in the electrolyzer supported upon a common,electrolyte-resistant structural member, in bipolar electrical andmechanical configuration with each other, the said structural memberhaving means for connecting said anodes and cathodes to said backplateand conducting electricity from said cathodes to said anodes of the saidnext adjacent cell, the improvement wherein said connecting andconducting means comprise:

a copper stud;

a steel sleeve on said copper stud;

a steel cap on the cathode end of said sleeve friction welded to saidcopper stud; and

a titanium stud friction welded to the opposite end of said copper studwherein the said cathodes are bonded to the steel cap on the cathode endof the said sleeve and copper stud, and the anodes are bonded to thetitanium stud on the anode end of said copper stud.

16. In a bipolar electrolyzer having a plurality of electrolytic cellsin series, with the cathodes of one cell and the anodes of the nextadjacent cell in the electrolyzer supported upon a common,electrolyte-resistant structural member, in bipolar electrical andmechanical configuration with each other, the said structural memberhaving means for connecting said anodes and cathodes to said backplateand conducting electricity from said cathodes to said anodes, theimprovement wherein said conducting and connection means pass throughsaid structural member and comprise:

a copper member;

a catholyte-resistant member bonded to the cathode facing end of saidcopper member; and

an anolyte-resistant member friction welded to the opposite end of saidcopper member, the friction welded bond between said anolyte-resistantmember and said copper member having an electrical conductivity ofgreater than about 1.5 X10 mho and having substantially no third phasevisible at 1000 magnification between the copper member and theanolyte-resistant member.

17. The bipolar electrolyzer of claim 16 wherein the saidanolyte-resistant member is a titanium member,

18. The bipolar electrolyzer of claim 16 wherein an anode is bonded tosaid anolyte-resistant member.

19. In a bipolar electrolyzer having a plurality of elcctrolytic cellsin series,-with the cathodes of one cell and the anodes of the nextadjacent cell in the electrolyzer supported upon a common,electrolyte-resistant structural member, in bipolar electrical andmechanical configuration with each other, the said structural memberhaving means for connecting said anodes and cathodes to said backplateand conducting electricity from said cathodes to said anodes, theimprovement wherein said conducting and connecting means pass throughsaid structural member and comprise:

a copper member;

a catholyte-resistant member friction welded to the cathode facing endof said copper member; and

an anolyte-resistant member bonded to the opposite end of said coppermember, the bond between said anolyte-resistant member and said coppermember having an electrical conductivity of greater than about 1.5 X10mho and having substantially no third phase visible at 1000magnification between the copper member and the anolyte-resistantmember.

20. The bipolar electrolyzer of claim 19 wherein the saidcatholyte-resistant member is a steel cap.

21. The bipolar electrolyzer of claim 19 wherein a cathode is bonded tosaid catholyte-resistant member.

References Cited UNITED STATES PATENTS 3,441,495 4/1969 Colman 204-4683,380,908 4/1968 Ono et al. 204290 F 1,592,512 7/ 1926 Allan 20'4-256GERALD L. KAPLAN, Primary Examiner W. I. SOLOMON, Assistant Examiner us.(:1. X.R. 204 2s4, 255, 256, 286

